Uses Services.jsm more and ready to test on mobile

* Since I started using Services.jsm, I decided to apply it more
uniformly and get it in other areas where it is useful.
* Moved the about: page component to a module, which is loaded
dynamically on mobile.
* Made the generated installers more reliable.
* Added small version of the add-on icon.
* This all needs testing on Windows, Linux and Android.